Capped poly(arylene ether) composition and process

ABSTRACT

A thermoset composition exhibiting reduced water absorption in the cured state includes an olefinically unsaturated monomer and a capped poly(arylene ether) prepared by the reaction of an uncapped poly(arylene ether) with an anhydride capping agent. The capped poly(arylene ether) is isolated and/or purified by methods that reduce the concentrations of polar impurities that contribute to water absorption by the cured composition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/678,243filed Oct. 3, 2003, which is incorporated in its entirety by referenceherein.

BACKGROUND OF THE INVENTION

Curable compositions with polymerizable poly(arylene ether) resins andco-monomers such as styrene and acrylate esters have been described, forexample, in U.S. Pat. No. 6,352,782 B2 to Yeager et al, and U.S. PatentApplication Publication No. 2001-0053820 A1 to Yeager et al. Onepotential use for such compositions is for fabricating plastic-packagedelectronic devices. Experience in the fabrication of these devices hassuggested the need for curable compositions that retain less water inthe cured state.

BRIEF DESCRIPTION OF THE INVENTION

One embodiment is a curable composition, comprising: an olefinicallyunsaturated monomer; and a capped poly(arylene ether) prepared by thereaction of an uncapped poly(arylene ether) with an anhydride cappingagent; wherein the composition after curing absorbs less than 1 weightpercent water after 7 days at 85° C. and 85 percent relative humidity.

Other embodiments, including a cured composition, an article comprisinga cured composition, and a method of preparing a curable composition,are described in detail below.

DETAILED DESCRIPTION OF THE INVENTION

One use of curable thermoset compositions is as a packaging material forplastic-packaged electronic devices. Manufacturing experience in thisfield has revealed that the electronic devices are sometimes damagedduring soldering by vaporization of water that has been absorbed by thecured thermoset composition. The resulting damage may includedelamination of plastic from the device, the device substrate, or otherinterfaces, as well as blistering of plastic above the device andcracking in the plastic packaging. To avoid these problems, devices aretypically baked to dryness immediately before assembly. In other cases,the electronic devices are handled in a dry nitrogen atmosphere. Thisexperience suggested a need for curable thermoset compositions thatexhibit reduced water absorption in the cured state. Such compositionswould allow simpler processes and improved efficiency in the manufactureof plastic-packaged electronic devices.

After extensive research, the present inventors have found that thewater retention of cured articles prepared from curable poly(aryleneether) compositions may depend on the method of preparation andisolation of the polymerized poly(arylene ether) macromer. Specifically,when the poly(arylene ether) with one or more capping groups (i.e., acapped poly(arylene ether)) is prepared by the reaction of an uncappedpoly(arylene ether) with an anhydride capping agent, the cappedpoly(arylene ether) may retain variable amounts of the anhydride cappingagent and its hydrolysis product(s), depending on the method ofpreparation. When an amine catalyst is used in the capping reaction, itspresence in the curable composition may also contribute to waterabsorption in the cured state. The amine catalyst may also form a saltwith a free acid hydrolysis product of the anhydride, either by reactionof the amine with the free acid or the anhydride itself. As demonstratedin the examples below, water absorption by the cured composition wasfound to increase with increasing amounts of these polar impurities. Thepresent inventors have found that various methods of reducing thesepolar impurities permit the formulation of a curable composition thatabsorbs less water in the cured state.

One embodiment is a curable composition, comprising: an olefinicallyunsaturated monomer; and a capped poly(arylene ether) prepared by thereaction of an uncapped poly(arylene ether) with an anhydride cappingagent; wherein the composition after curing absorbs less than 1 weightpercent water after 7 days at 85° C. and 85 percent relative humidity.

The curable composition includes a capped poly(arylene ether) preparedby the reaction of an uncapped poly(arylene ether) with an anhydridecapping agent. A capped poly(arylene ether) is defined herein as apoly(arylene ether) in which at least 50%, preferably at least 75%, morepreferably at least 90%, yet more preferably at least 95%, even morepreferably at least 99%, of the free hydroxyl groups present in thecorresponding uncapped poly(arylene ether) have been finctionalized byreaction with a capping agent. The capped poly(arylene ether) may berepresented by the structureQ(J-K)_(y)wherein Q is the residuum of a monohydric, dihydric, or polyhydricphenol, preferably the residuum of a monohydric or dihydric phenol, morepreferably the residuum of a monohydric phenol; y is 1 to 100; Jcomprises repeating structural units having the formula

wherein m is 1 to about 200, preferably 2 to about 200, and R¹ and R³are each independently hydrogen, halogen, primary or secondary C₁-C₁₂alkyl, C₂-C₁₂ alkenyl, C₂-C₁₂ alkynyl, C₁-C₁₂ aminoalkyl, C₁-C₁₂hydroxyalkyl, phenyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ hydrocarbyloxy, C₂-C₁₂halohydrocarbyloxy wherein at least two carbon atoms separate thehalogen and oxygen atoms, or the like; R² and R⁴ are each independentlyhalogen, primary or secondary C₁-C₁₂ alkyl, C₂-C₁₂ alkenyl, C₂-C₁₂alkynyl, C₁-C₁₂ aminoalkyl, C₁-C₁₂ hydroxyalkyl, phenyl, C₁-C₁₂haloalkyl, C₁-C₁₂ hydrocarbyloxy, C₂-C₁₂ halohydrocarbyloxy wherein atleast two carbon atoms separate the halogen and oxygen atoms, or thelike; and K is a capping group produced by reaction of a free phenolichydroxyl group on the poly(arylene ether) with an anhydride cappingagent. The resulting capping group may be

or the like, wherein R⁵ is C₁-C₁₂ hydrocarbyl optionally substitutedwith one or two carboxylic acid groups, or the like; R⁶—R⁸ are eachindependently hydrogen, C₁-C₁₈ hydrocarbyl optionally substituted withone or two carboxylic acid groups, C₂-C₁₈ hydrocarbyloxycarbonyl,nitrile, formyl, carboxylic acid, imidate, thiocarboxylic acid, or thelike; and R⁹—R¹³ are each independently hydrogen, halogen, C₁-C₁₂ alkyl,hydroxy, amino, carboxylic acid (—CO₂H), or the like. As used herein,“hydrocarbyl” refers to a residue that contains only carbon andhydrogen. The residue may be aliphatic or aromatic, straight-chain,cyclic, bicyclic, branched, saturated, or unsaturated. The hydrocarbylresidue, when so stated however, may contain heteroatoms over and abovethe carbon and hydrogen members of the substituent residue. Thus, whenspecifically noted as containing such heteroatoms, the hydrocarbylresidue may also contain carbonyl groups, amino groups, hydroxyl groups,halogen atoms, or the like, or it may contain heteroatoms within thebackbone of the hydrocarbyl residue.

In one embodiment, Q is the residuum of a phenol, includingpolyfunctional phenols, and includes radicals of the structure

wherein R¹ and R³ are each independently hydrogen, halogen, primary orsecondary C₁-C₁₂ alkyl, C₂-C₁₂ alkenyl, C₂-C₁₂ alkynyl, C₁-C₁₂aminoalkyl, C₁-C₁₂ hydroxyalkyl, phenyl, C₁-C₁₂ haloalkyl, C₁-C₁₂aminoalkyl, C₁-C₁₂ hydrocarbyloxy, C₂-C₁₂ halohydrocarbyloxy wherein atleast two carbon atoms separate the halogen and oxygen atoms, or thelike; R² and R⁴ are each independently halogen, primary or secondaryC₁-C₁₂ alkyl, C₂-C₁₂ alkenyl, C₂-C₁₂ alkynyl, C₁-C₁₂ aminoalkyl, C₁-C₁₂hydroxyalkyl, phenyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ aminoalkyl, C₁-C₁₂hydrocarbyloxy, C₂-C₁₂ halohydrocarbyloxy wherein at least two carbonatoms separate the halogen and oxygen atoms, or the like; X may behydrogen, C₁-C₁₈ hydrocarbyl, or C₁-C₁₈ hydrocarbyl containing asubstituent such as carboxylic acid, aldehyde, alcohol, amino radicals,or the like; X also may be sulfur, sulfonyl, sulfuryl, oxygen, or othersuch bridging group having a valence of 2 or greater to result invarious bis- or higher polyphenols; n (i.e., the number of phenyleneether units bound to X) is 1 to about 100, preferably 1 to 3, and morepreferably 1 to 2. Q may be the residuum of a monohydric phenol, such as2,6-dimethylphenol, in which case n is 1. Q may also be the residuum ofa diphenol, such as 2,2′,6,6′-tetramethyl-4,4′-diphenol, in which case nis 2.

The uncapped poly(arylene ether) may be defined by reference to thecapped poly(arylene ether) Q(J-K)_(y) as Q(J-H)_(y), where Q, J and yare defined above, and a hydrogen atom, H, has taken the place of anycapping group, K. In one embodiment, the uncapped poly(arylene ether)consists essentially of the polymerization product of at least onemonohydric phenol having the structure

wherein R¹ and R³ are each independently hydrogen, halogen, primary orsecondary C₁-C₁₂ alkyl, C₂-C₁₂ alkenyl, C₂-C₁₂ alkynyl, C₁-C₁₂aminoalkyl, C₁-C₁₂ hydroxyalkyl phenyl, C₁-C₁₂ haloalkyl, C₁-C₁₂aminoalkyl, C₁-C₁₂ hydrocarbyloxy, C₂-C₁₂ halohydrocarbyloxy wherein atleast two carbon atoms separate the halogen and oxygen atoms, or thelike; and R² and R⁴ are each independently halogen, primary or secondaryC₁-C₁₂ alkyl, C₂-C₁₂ alkenyl, C₂-C₁₂ alkynyl, C₁-C₁₂ aminoalkyl, C₁-C₁₂hydroxyalkyl, phenyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ aminoalkyl, C₁-C₁₂hydrocarbyloxy, C₂-C₁₂ halohydrocarbyloxy wherein at least two carbonatoms separate the halogen and oxygen atoms, or the like. Suitablemonohydric phenols include those described, for example, in U.S. Pat.No. 3,306,875 to Hay, and highly preferred monohydric phenols include2,6-dimethylphenol and 2,3,6-trimethylphenol. The poly(arylene ether)may be a copolymer of at least two monohydric phenols, such as2,6-dimethylphenol and 2,3,6-trimethylphenol. Thus, the uncappedpoly(arylene ether) may comprise poly(2,6-dimethyl-1,4-phenylene ether),poly(2,6-dimethyl-1,4-phenylene ether-co-2,3,6-trimethyl-1,4-phenyleneether), or a mixture thereof. In one embodiment, the uncappedpoly(phenylene ether) is isolated by precipitation and preferably hasless than about 400 parts per million of organic impurities and morepreferably less than about 300 parts per million. Organic impuritiesinclude, for example, 2,3-dihydrobenzofuran, 2,4,6-trimethylanisole,2,6-dimethylcyclohexanone, 7-methyl-2,3-dihydrobenzofuran, and the like.

In one embodiment, the capped poly(arylene ether) comprises at least onecapping group having the structure

wherein R⁶—R⁸ are each independently hydrogen, C₁-C₁₈ hydrocarbyl,C₂-C₁₈ hydrocarbyloxycarbonyl, nitrile, formyl, carboxylic acid,imidate, thiocarboxylic acid, or the like. Highly preferred cappinggroups include acrylate (R⁶═R⁷═R⁸=hydrogen) and methacrylate (R⁶=methyl,R⁷═R⁸=hydrogen). It will be understood that the term “(meth)acrylate”means either acrylate or methacrylate.

In another embodiment, the capped poly(arylene ether) comprises at leastone capping group having the structure

wherein R⁵ is C₁-C₁₂ hydrocarbyl optionally substituted with one or twocarboxylic acid groups, or the like, preferably C₁-C₆ alkyl, morepreferably methyl, ethyl, or isopropyl. The advantageous properties ofthe invention can be achieved even when the capped poly(arylene ether)lacks a polymerizable function such as a carbon-carbon double bond.

In yet another embodiment, the capped poly(arylene ether) comprises atleast one capping group having the structure

wherein R⁹—R¹³ are each independently hydrogen, halogen, C₁-C₁₂ allyl,hydroxy, amino, carboxylic acid, or the like. Preferred capping groupsof this type include salicylate (R⁹=hydroxy, R¹⁰—R¹³=hydrogen).

The capped poly(arylene ether) is formed by the reaction of an uncappedpoly(arylene ether) with an anhydride capping agent. In one embodiment,the anhydride capping agent may have the structure

wherein each occurrence of Y is independently

or the like, wherein R⁵ is C₁-C₁₂ hydrocarbyl optionally substitutedwith one or two carboxylic acid groups, or the like; R⁶—R⁸ are eachindependently hydrogen, C₁-C₁₈ hydrocarbyl, C₂-C₁₈hydrocarbyloxycarbonyl, nitrile, formyl, carboxylic acid, imidate, orthiocarboxylic acid; and R⁹—R¹³ are each independently hydrogen,halogen, C₁-C₁₂ alkyl, hydroxy, amino, amino, carboxylic acid, or thelike. Examples of suitable anhydride capping agents include, forexample, acetic anhydride, succinic anhydride, maleic anhydride,salicylic anhydride, phthalic anhydride, acrylic anhydride, methacrylicanhydride, and the like, and combinations thereof. It will be understoodthat the anhydride capping agent further includes diacids capable offorming the corresponding cyclic anhydride under the capping reactionconditions. Such diacids include, for example, maleic acid, malic acid,citraconic acid, itaconic acid, phthalic acid, and the like.

In one embodiment, the anhydride capping agent has the structure

wherein each occurrence of R⁶—R⁸ is C₁-C₁₈ hydrocarbyl, C₂-C₁₂hydrocarbyloxycarbonyl, nitrile, formyl, carboxylic acid, imidate,thiocarboxylic acid, or the like. In another embodiment, the anhydridecapping agent comprises acrylic anhydride, methacrylic anhydride, or amixture thereof.

Methods of reacting an uncapped poly(arylene ether) with an anhydridecapping agent are described, for example, in U.S. Pat. No. 3,375,228 toHoloch et al., U.S. Pat. No. 4,148,843 to Goossens, U.S. Pat. No.4,806,602 to White et al., U.S. Pat. No. 5,219,951 to Nelissen et al.,U.S. Pat. No. 6,384,176 to Braat et al; U.S. Patent ApplicationPublication No. 2001/0053820 A1 to Yeager et al.; and European PatentNo. 261,574 B1 to Peters et al.

In one embodiment, the curable composition includes an alkenyl aromaticmonomer, and the capped poly(arylene ether) is prepared by reaction ofan uncapped poly(arylene ether) with an anhydride in the alkenylaromatic monomer as solvent.

There is no particular limitation on the molecular weight or intrinsicviscosity of the capped poly(arylene ether). In one embodiment, thecomposition may comprise a capped poly(arylene ether) having a numberaverage molecular weight of about 1,000 to about 25,000 atomic massunits (AMU). Within this range, it may be preferable to use a cappedpoly(arylene ether) having a number average molecular weight of at leastabout 2,000 AMU, more preferably at least about 4,000 AMU. In anotherembodiment, the composition may comprise a capped poly(arylene ether)having an intrinsic viscosity of about 0.05 to about 0.6 deciliters pergram (dL/g) as measured in chloroform at 25° C. Within this range, thecapped poly(arylene ether) intrinsic viscosity may preferably be atleast about 0.08 dL/g, more preferably at least about 0.1 dL/g. Alsowithin this range, the capped poly(arylene ether) intrinsic viscositymay preferably be up to about 0.5 dL/g, still more preferably up toabout 0.4 dL/g, even more preferably up to about 0.3 dL/g. Generally,the intrinsic viscosity of a capped poly(arylene ether) will varyinsignificantly from the intrinsic viscosity of the correspondinguncapped poly(arylene ether). Specifically, the intrinsic viscosity of acapped poly(arylene ether) will generally be within 10% of that of theuncapped poly(arylene ether). It is expressly contemplated to employblends of at least two capped poly(arylene ether)s having differentmolecular weights and intrinsic viscosities. The composition maycomprise a blend of at least two functionalized poly(arylene ethers).Such blends may be prepared from individually prepared and isolatedfunctionalized poly(arylene ethers). Alternatively, such blends may beprepared by reacting a single poly(arylene ether) with at least twofunctionalizing agents. For example, a poly(arylene ether) may bereacted with two capping agents, or a poly(arylene ether) may bemetallized and reacted with two unsaturated alkylating agents. Inanother alternative, a mixture of at least two poly(arylene ether)resins having different monomer compositions and/or molecular weightsmay be reacted with a single functionalizing agent. The composition may,optionally, comprise a blend of a capped poly(arylene ether) resin andan uncapped poly(arylene ether) resin, and these two components may,optionally, have different intrinsic viscosities.

A capping catalyst may be employed in the reaction of an uncappedpoly(arylene ether) with an anhydride. Examples of such compoundsinclude those known to the art that are capable of catalyzingcondensation of phenols with the capping agents described above. Usefulmaterials include, but are not limited to, basic compounds including,for example, hydroxide salts such as sodium hydroxide, potassiumhydroxide, tetraalkylammonium hydroxides, and the like; tertiaryalkylamines such as tributylamine, triethylamine, dimethylbenzylamine,dimethylbutylamine and the like; tertiary mixed alkyl-arylamines andsubstituted derivatives thereof such as N,N-dimethylaniline;heterocyclic amines such as imidazoles, pyridines, and substitutedderivatives thereof such as 2-methylimidazole, 2-vinylimidazole,4-dimethylaminopyridine, 4-(1-pyrrolino)pyridine,4-(1-piperidino)pyridine, 2-vinylpyridine, 3-vinylpyridine,4-vinylpyridine, and the like. Also useful are organometallic salts suchas, for example, tin and zinc salts known to catalyze the condensationof, for example, isocyanates or cyanate esters with phenols. Theorganometallic salts useful in this regard are known to the art innumerous publications and patents well known to those skilled in thisart.

In one embodiment, the capping catalyst is an organic amine catalyst.Preferred organic amine catalysts include, for example, tertiaryalkylamines, tertiary mixed alkyl-aryl amines, heterocyclic amines, andthe like. It will be understood that the organic amine catalyst includesammonium ions formed by protonation of the organic amine. In oneembodiment, the capping catalyst comprises a 4-dialkylaminopyridinehaving the structure

wherein R²³ and R²⁴ are each independently hydrogen or C₁-C₆ alkyl, andR²⁵ and R²⁶ are each independently C₁-C₆ alkyl. In a preferredembodiment, the capping catalyst comprises 4-dimethylaminopyridine(DMAP).

The curable composition may comprise about 5 to about 90 parts by weightof the capped poly(arylene ether) per 100 parts by weight total of thecapped poly(arylene ether) and the olefinically unsaturated monomer.Within this range, the amount of the capped poly(arylene ether) resinmay preferably be at least about 10 parts by weight, more preferably atleast about 15 parts by weight. Also within this range, the amount ofthe capped poly(arylene ether) resin may preferably be up to about 80parts by weight, more preferably up to about 60 parts by weight, stillmore preferably up to about 50 parts by weight.

The curable composition includes an olefinically unsaturated monomer.The olefinically unsaturated monomer is herein defined as apolymerizable monomer comprising a carbon-carbon double bound. Suitableolefinically unsaturated monomers include, for example, alkenyl aromaticmonomers, allylic monomers, acryloyl monomers, and the like, andmixtures thereof.

The alkenyl aromatic monomer may have the formula

wherein each occurrence of R¹⁶ is independently hydrogen or C₁-C₁₈hydrocarbyl; each occurrence of R¹⁷ is independently halogen, C₁-C₁₂alkyl, C₁-C₁₂ alkoxyl, or C₆-C₁₈ aryl; p is 1 to 4; and q is 0 to 5.Unspecified positions on the aromatic ring are substituted with hydrogenatoms. Suitable alkenyl aromatic monomers include, for example, styrene,α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene,2-t-butylstyrene, 3-t-butylstyrene, 4-t-butylstyrene,1,3-divinylbenzene, 1,4-divinylbenzene, 1,3-diisopropenylbenzene,1,4-diisopropenylbenzene, styrenes having from 1 to 5 halogensubstituents on the aromatic ring, and the like, and combinationsthereof. Styrene is a particularly preferred alkenyl aromatic monomer.

The olefinically unsaturated monomer may be an allylic monomer. Anallylic monomer is an organic compound comprising at least one,preferably at least two, more preferably at least three allyl(—CH₂—CH═CH₂) groups. Suitable allylic monomers include, for example,diallyl phthalate, diallyl isophthalate, triallyl mellitate, triallylmesate, triallyl benzenes, triallyl cyanurate, triallyl isocyanurate,mixtures thereof, partial polymerization products prepared therefrom,and the like.

The olefinically unsaturated monomer may be an acryloyl monomer. Anacryloyl monomer is a compound comprising at least one acryloyl moietyhaving the structure

wherein R²⁰—R²² are each independently hydrogen, C₁-C₁₂ hydrocarbyl,C₂-C₁₈ hydrocarbyloxycarbonyl, nitrile, formyl, carboxylic acid,imidate, thiocarboxylic acid, or the like. In one embodiment, theacryloyl monomer comprises at least two acryloyl moieties. In anotherembodiment, the acryloyl monomer comprises at least three acryloylmoieties. Suitable acryloyl monomers include, for example,trimethylolpropane tri(meth)acrylate, 1,6-hexanediol di(meth)acrylate,neopentyl glycol di(meth)acrylate, ethylene glycol di(meth)acrylate,propylene glycol di(meth)acrylate, cyclohexanedimethanoldi(meth)acrylate, butanediol di(meth)acrylate, diethylene glycoldi(meth)acrylate, triethylene glycol di(meth)acrylate,isobornyl(meth)acrylate, methyl(meth)acrylate, methacryloxypropyltrimethoxysilane (also known as 3-(trimethoxysilyl)propyl methacrylate),ethoxylated(2)bisphenol A di(meth)acrylate (it will be understood thatthe number following the ethoxylated term refers to the average numberof ethoxy groups in the ethoxylate chain attached to each oxygen ofbisphenol A), and the like, and mixtures comprising at least one of theforegoing acryloyl monomers.

In one embodiment, the olefinically unsaturated monomer comprisesstyrene and trimethylolpropane trimethacrylate.

The composition may generally comprise about 10 to about 95 parts byweight of the olefinically unsaturated monomer per 100 parts by weighttotal of the capped poly(arylene ether) and the olefinically unsaturatedmonomer. Within this range, it may be preferable to use an olefinicallyunsaturated monomer amount of at least about 20 parts by weight, morepreferably at least about 30 parts by weight. Also within this range, itmay be preferable to use an olefinically unsaturated monomer amount ofup to about 80 parts per weight, more preferably up to about 60 parts byweight.

The composition after curing absorbs less than about 1 weight percent,preferably less than about 0.5 weight percent, more preferably less thanabout 0.3 weight percent, even more preferably less than about 0.2weight percent, of water after seven days exposure to 85° C. and 85%relative humidity. The present inventors believe that such low levels ofwater absorption have not been achieved by previously disclosedpoly(arylene ether) curable compositions. The present inventors havediscovered that water absorption by the cured composition may be reducedif the capped poly(arylene ether) is isolated and/or purified by amethod that reduces the residual concentration of one or more of thefollowing capping-related reagents and by-products: anhydride cappingagent, free acid(s) obtained on hydrolysis of the anhydride cappingagent, organic amine, and salts formed between organic amine and theanhydride capping agent or its free acid hydrolysis product. Reducedwater absorption is typically associated with beneficial propertiesincluding higher glass transition temperature under high humidityconditions, lower coefficient of thermal expansion under high humidityconditions, greater flexural strength at high humidity conditions, andgreater toughness under high humidity conditions.

In one embodiment, the composition comprises less than 50, preferablyless than 30, more preferably less than 10, parts per million of theanhydride capping agent, based on the weight of the capped poly(aryleneether). Previous descriptions of capped poly(arylene ether) resins andcurable compositions containing them did not recognize the importance ofreducing the concentrations of residues comprising anhydride, nor didthey teach methods of attaining such low concentrations. The lowanhydride concentrations may be achieved by a variety of methods. Forexample, as shown in the working examples, precipitation of the cappedpoly(arylene ether) by combining the capping reaction mixture with aC₂-C₆ alkanol, such as isopropanol, yields unexpectedly low anhydrideconcentrations. Suitable C₂-C₆ alkanols include, for example, ethanol,n-propanol, isopropanol, 1-butanol, 2-butanol, 2-methyl-1-propanol(isobutanol), 2-methyl-2-propanol (t-butanol), 1-pentanol, 2-pentanol,3-pentanol, 2-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol,3-methyl-1-butanol, 2,2-dimethyl-1-propanol, cyclopentanol, 1-hexanol,2-hexanol, 3-hexanol, 5-methyl-1-pentanol, 5-methyl-2-pentanol,2-methyl-3-pentanol, 2-methyl-2-pentanol, 2-methyl-1-pentanol,3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol,2-ethyl-1-butanol, 2,2-dimethyl-1-butanol, 3,3-dimethyl-2-butanol,3,3-dimethyl-1-butanol, 2,3-dimethyl-1-butanol, 2,3-dimethyl-2-butanol,1-methylcyclopentanol, 2-methylcyclopentanol, 3-methylcyclopentanol,cyclopentylmethanol, cyclohexanol, and the like, and mixtures thereof. Apreferred C₂-C₆ alkanol is isopropanol. While not necessarily sufficientto achieve an anhydride concentration less than 50 parts per million byweight (ppm), precipitations with other antisolvents may achievesubstantial reductions in anhydride concentration. Such otherantisolvents include, for example, methanol, ketones having three toabout ten carbon atoms, alkanes having five to about ten carbon atoms,and the like, and mixtures thereof. Substantial reductions in anhydrideconcentration, as well as the concentrations of other impurities, mayalso be achieved by washing the capping reaction mixture with an aqueoussolution. The aqueous solution includes water and may, optionally,include acids, bases, or salts to facilitate extraction and/orconversion of anhydride from the capped poly(arylene ether) solution. Asone example, the aqueous wash may have a pH of about 1 to about 7. Asanother example, the aqueous wash may have a pH of about 7 to about 13.As another example, the water wash may contain sodium hydroxide at about0.0001 to about 1 normal to facilitate extraction of free acids, andhydrolysis and extraction of anhydrides. As another example, the waterwash may contain hydrochloric acid at 0.0001 to about 1 normal tofacilitate extraction of basic species, such as 4-dimethylaminopyridine.Efficient extraction of both basic and acidic impurities may be effectedwith sequential washes in acid and base, or vice versa. For example, awash at an acidic pH (e.g., a pH of about 1 to 7) and buffer strengthsufficient to remove substantially all basic residues may be followed bya wash at a basic pH (e.g., a pH of about 7 to about 13) and a bufferstrength sufficient to remove substantially all acidic residues, wherein“substantially all” in various embodiments means greater than about 90wt. %, or greater than about 95 wt. %, or greater than about 98 wt. % orgreater than about 99 wt. %, or greater than about 99.5 wt. % based onthe weight of residue originally present. In one embodiment, essentiallyall of said residue is removed meaning that the residue cannot bedetected using normal analytical techniques. Another method forachieving substantial reductions in anhydride concentration is bydevolatilization of a capping reaction mixture. Devolatilization methodsare described, for example, in U.S. Pat. No. 6,384,176 B2 to Braat etal. Although the devolatilization methods previously taught do notappear to be sufficient to achieve an anhydride concentration of lessthan 50 ppm, that level may be achieved by the use of devolatilizationin combination with a pre-treatment, such as aqueous washing.

The above methods for reducing the anhydride concentration may have theadditional benefit of reducing the concentrations of other polarimpurities. For example, they may reduce the concentration of free acidderived from anhydride hydrolysis to less than about 1 weight percent,preferably less than about 0.8 weight percent, more preferably less thanabout 0.7 weight percent, based on the weight of the capped poly(aryleneether). When the anhydride is acyclic and symmetrical, as is preferred,its hydrolysis generates two molecules of free acid. When the anhydrideis acyclic and unsymmetrical, “a free acid” in the above limitationcorresponds to either of the two acids formed by anhydride hydrolysis.When the anhydride is cyclic, its hydrolysis generates one molecule of adicarboxylic acid, and “a free acid” in the above limitation correspondsto the dicarboxylic acid. Thus, one embodiment is a curable composition,comprising: an olefinically unsaturated monomer; and a cappedpoly(arylene ether) prepared by the reaction of an uncapped poly(aryleneether) with an anhydride capping agent; wherein the compositioncomprises less than 1 weight percent of a free acid obtained onhydrolysis of the anhydride capping agent, based on the weight of thecapped poly(arylene ether). The above methods for reducing the anhydrideconcentration may also reduce the concentration of any organic aminepresent. Specifically, the above methods may reduce the organic amineconcentration to less than about 1,000 parts per million, preferablyless than about 600 parts per million, more preferably less than about400 parts per million, based on the weight of the capped poly(aryleneether). For example, when capping of poly(2,6-dimethyl-1,4-phenyleneether) with methacrylic anhydride is catalyzed by4-dimethylaminopyridine (DMAP), treatment of the reaction mixture asdescribed above may reduce the residual concentration of DMAP to lessthan about 1,000 parts per million.

Another embodiment is a curable composition, comprising an olefinicallyunsaturated monomer; a particulate filler; and a capped poly(aryleneether) prepared by the reaction of an uncapped poly(arylene ether) withan anhydride capping agent; wherein the capped poly(arylene ether) isisolated by a procedure comprising precipitation with a C₂-C₆ alkanol;wherein the composition after curing absorbs less than 0.5 weightpercent water after 7 days at 85° C. and 85 percent relative humidity.

Another embodiment is a curable composition, comprising about 1 to about23 weight percent of a methacrylate-cappedpoly(2,6-dimethyl-1,4-phenylene ether) prepared by the reaction of anuncapped poly(2,6-dimethyl-1,4-phenylene ether) with methacrylicanhydride; wherein the methacrylate-cappedpoly(2,6-dimethyl-1,4-phenylene ether) is isolated by a procedurecomprising precipitation with isopropanol; about 1 to about 23 weightpercent of an acryloyl monomer comprising at least two acryloylmoieties; about 1 to about 23 weight percent of an alkenyl aromaticmonomer selected from styrene, α-methylstyrene, 2-methylstyrene,3-methylstyrene, 4-methylstyrene, 2-t-butylstyrene, 3-t-butylstyrene,4-t-butylstyrene, 1,3-divinylbenzene, 1,4-divinylbenzene,1,3-diisopropenylbenzene, 1,4-diisopropenylbenzene, styrenes having from1 to 5 halogen substituents on the aromatic ring, and combinationsthereof; and about 75 to about 95 weight percent of fused silica;wherein all weight percents are based on the total weight of thecomposition; and wherein the composition after curing absorbs less than0.2 weight percent water after 7 days at 85° C. and 85 percent relativehumidity. Preferred acryloyl monomers include trimethylolpropanetrimethacrylate and ethoxylated (2) bisphenol A dimethacrylate.

The curable composition may, optionally, further comprise a curingcatalyst to increase the curing rate of the unsaturated components.Curing catalysts, also referred to as initiators, are well known to theart and may be used to initiate the polymerization, curing, orcrosslinking of numerous thermoplastics and thermosets includingunsaturated polyester, vinyl ester and allylic thermosets. Non-limitingexamples of curing catalysts are those described in U.S. Pat. No.5,407,972 to Smith et al., and U.S. Pat. No. 5,218,030 to Katayose etal. The curing catalyst for the unsaturated portion of the thermoset mayinclude any compound capable of producing free radicals at elevatedtemperatures. Such curing catalysts may include both peroxy andnon-peroxy based radical initiators. Examples of useful peroxyinitiators include, for example, benzoyl peroxide, dicumyl peroxide,methyl ethyl ketone peroxide, lauryl peroxide, cyclohexanone peroxide,t-butyl hydroperoxide, t-butyl benzene hydroperoxide, t-butylperoctoate, 2,5-dimethylhexane-2,5-dihydroperoxide,2,5-dimethyl-2,5-di(t-butylperoxy)-hex-3-yne, di-t-butylperoxide,t-butylcumyl peroxide, α,α′-bis(t-butylperoxy-m-isopropyl)benzene,2,5-dimethyl-2,5-di(t-butylperoxy)hexane, di(t-butylperoxy)isophthalate,t-butylperoxybenzoate, 2,2-bis(t-butylperoxy)butane,2,2-bis(t-butylperoxy)octane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane,di(trimethylsilyl)peroxide, trimethylsilylphenyltriphenylsilyl peroxide,and the like, and mixtures comprising at least one of the foregoingcuring catalysts. Typical non-peroxy initiators include, for example,2,3-dimethyl-2,3-diphenylbutane,2,3-trimethylsilyloxy-2,3-diphenylbutane, and the like, and mixturescomprising at least one of the foregoing curing catalysts. The curingcatalyst for the unsaturated portion of the thermoset may furtherinclude any compound capable of initiating anionic polymerization of theunsaturated components. Such anionic polymerization catalysts include,for example, alkali metal amides, such as sodium amide (NaNH₂) andlithium diethyl amide (LiN(C₂H₅)₂); alkali metal and ammonium salts ofC₁-C₁₀ alkoxides; alkali metal and ammonium hydroxides; alkali metalcyanides; organometallic compounds such as the alkyl lithium compoundn-butyl lithium and the Grignard reagent phenyl magnesium bromide; andthe like; and combinations comprising at least one of the foregoinganionic polymerization catalysts. In a preferred embodiment, the curingcatalyst may comprise t-butylperoxybenzoate or dicumyl peroxide. Thecuring catalyst may promote curing at a temperature in a range of about0° C. to about 200° C.

When present, the curing catalyst may be used in an amount of about 0.1to about 10 parts by weight per 100 parts total of the cappedpoly(arylene ether) and the olefinically unsaturated monomer. Withinthis range, it may be preferred to use a curing catalyst amount of atleast about 0.5 parts by weight, more preferably at least about 1 partby weight. Also within this range, it may be preferred to use a curingcatalyst amount of up to about 5 parts by weight, more preferably up toabout 3 parts by weight.

The curable composition may, optionally, further comprise a curingpromoter to decrease the gel time. Suitable curing promoters includetransition metal salts and complexes such as cobalt naphthanate; andorganic bases such as N,N-dimethylaniline (DMA) and N,N-diethylaniline(DEA). Preferably, cobalt naphthanate and DMA are used in combination.When present, the promoter may be used in an amount of about 0.05 toabout 3 parts, per 100 parts total of the capped poly(arylene ether) andthe olefinically unsaturated monomer.

The composition may, optionally, further comprise a curing inhibitor,which functions to prevent premature curing of the composition. Suitablecuring inhibitors include, for example, diazoaminobenzene,phenylacetylene, symtrinitrobenzene, p-benzoquinone, acetaldehyde,aniline condensates, N,N′-dibutyl-o-phenylenediamine,N-butyl-p-aminophenol, p-methoxyphenol, 2,4,6-triphenylphenoxyl,pyrogallol, catechol, hydroquinone, monoallcyllydroquinones,t-butylhydroquinone, C₁-C₆-allyl-substituted catechols,dialkylhydroquinones, 2,4,6-dichloronitrophenol,halogen-ortho-nitrophenols, alkcoxyhydroquinones, mono- and di- andpolysulfides of phenols and catechols, thiols, oximes and hydrazones ofquinone, phenothiazine, diarcylhydroxylamines, and the like, andcombinations comprising at least one of the foregoing curing inhibitors.Suitable curing inhibitors further include uncapped poly(arylene ether)s(i.e., poly(arylene ether)s having free hydroxyl groups). Preferredcuring inhibitors include benzoquinone, hydroquinone, andtert-butylcatechol. When present, the curing inhibitor amount may beabout 0.01 to about 10 parts by weight, per 100 parts by weight total ofthe capped poly(arylene ether) resin and the olefinically unsaturatedmonomer. Within this range, the curing inhibitor amount may preferablybe at least about 0.1 part by weight. Also within this range, the curinginhibitor amount may preferably be up to about 2 parts by weight.

The composition may further comprise one or more fillers, includingparticulate fillers and fibrous fillers. Examples of such fillers arewell known in the art and include those described in “Plastic AdditivesHandbook, 4^(th) Edition” R. Gachter and H. Muller (eds.), P. P.Klemchuck (assoc. ed.) Hanser Publishers, New York 1993, pages 901-948.A particulate filler is herein defined as a filler having an averageaspect ratio less than about 5:1. Non-limiting examples of fillersinclude silica powder, such as fused silica and crystalline silica;boron-nitride powder and boron-silicate powders for obtaining curedproducts having high thermal conductivity, low dielectric constant andlow dielectric loss tangent; the above-mentioned powder as well asalumina, and magnesium oxide (or magnesia) for high temperatureconductivity; and fillers, such as wollastonite includingsurface-treated wollastonite, calcium sulfate (in its anhydrous,hemihydrated, dihydrated, or trihydrated forms), calcium carbonateincluding chalk, limestone, marble and synthetic, precipitated calciumcarbonates, generally in the form of a ground particulate which oftencomprises 98+% CaCO₃ with the remainder being other inorganics such asmagnesium carbonate, iron oxide, and alumino-silicates; surface-treatedcalcium carbonates; talc, including fibrous, nodular, needle shaped, andlamellar talc; glass spheres, both hollow and solid, and surface-treatedglass spheres typically having coupling agents such as silane couplingagents and/or containing a conductive coating; and kaolin, includinghard, soft, calcined kaolin, and kaolin comprising various coatingsknown to the art to facilitate the dispersion in and compatibility withthe thermoset resin; mica, including metallized mica and mica surfacetreated with aminosilane or acryloylsilane coatings to impart goodphysical properties to compounded blends; feldspar and nephelinesyenite; silicate spheres; flue dust; cenospheres; fillite;aluminosilicate (armospheres), including silanized and metallizedaluminosilicate; natural silica sand; quartz; quartzite; perlite;Tripoli; diatomaceous earth; synthetic silica, including those withvarious silane coatings, and the like.

Preferred particulate fillers include fused silica having an averageparticle size of about 1 to about 50 micrometers. A particularlypreferred particulate filler comprises a first fused silica having amedian particle size of about 0.03 micrometer to less than 1 micrometer,and a second fused silica having a median particle size of at least 1micrometer to about 30 micrometers. The preferred fused silicas haveessentially spherical particles, typically achieved by re-melting.Within the size range specified above, the first fused silica maypreferably have a median particle size of at least about 0.1 micrometer,preferably at least about 0.2 micrometer. Also within the size rangeabove, the first fused silica may preferably have a median particle sizeof up to about 0.9 micrometer, more preferably up to about 0.8micrometer. Within the size range specified above, the second fusedsilica may preferably have a median particle size of at least about 2micrometers, preferably at least about 4 micrometers. Also within thesize range above, the second fused silica may preferably have a medianparticle size of up to about 25 micrometers, more preferably up to about20 micrometers. In one embodiment, the composition comprises the firstfused silica and the second fused silica in a weight ratio in a range ofabout 70:30 to about 99:1, preferably in a range of about 80:20 to about95:5.

Fibrous fillers include short inorganic fibers, including processedmineral fibers such as those derived from blends comprising at least oneof aluminum silicates, aluminum oxides, magnesium oxides, and calciumsulfate hemihydrate. Also included among fibrous fillers are singlecrystal fibers or “whiskers” including silicon carbide, alumina, boroncarbide, carbon, iron, nickel, copper. Also included among fibrousfillers are glass fibers, including textile glass fibers such as E, A,C, ECR, R, S, D, and NE glasses and quartz. Preferred fibrous fillersinclude glass fibers having a diameter in a range of about 5 to about 25micrometers and a length before compounding in a range of about 0.5 toabout 4 centimeters. Many other suitable fillers are described in U.S.Patent Application Publication No. 2001/0053820 A1 to Yeager et al.

The formulation may also contain adhesion promoters to improve adhesionof the thermosetting resin to the filler or to an external coating orsubstrate. Also possible is treatment of the aforementioned inorganicfillers with adhesion promoter to improve adhesion. Adhesion promotersinclude chromium complexes, silanes, titanates, zirco-aluminates,propylene maleic anhydride copolymers, reactive cellulose esters and thelike. Chromium complexes include those sold by DuPont under thetradename VOLAN®. Silanes include molecules having the general structure(RO)_((4-n))SiY_(n) wherein n=1-3, R is an alkyl or aryl group and Y isa reactive functional group which can enable formation of a bond with apolymer molecule. Particularly useful examples of coupling agents arethose having the structure (RO)₃SiY. Typical examples include vinyltriethoxysilane, vinyl tris(2-methoxy)silane, phenyl trimethoxysilane,γ-methacryloxypropyltrimethoxy silane, γ-aminopropyltriethoxysilane,γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, andthe like. Silanes further include molecules lacking a reactivefunctional group, such as, for example, trimethoxyphenylsilane.Titanates include those developed by S. J. Monte et al. in Ann. Chem.Tech Conf. SPI (1980), Ann. Tech Conf. Reinforced Plastics and CompositeInst. SPI 1979, Section 16E, New Orleans; and S. J. Monte, Mod. PlasticsInt., volume 14, number 6 pg. 2 (1984). Zirco-aluminates include thosedescribed by L. B. Cohen in Plastics Engineering, volume 39, number 11,page 29 (1983). The adhesion promoter may be included in thethermosetting resin itself, or coated onto any of the fillers describedabove to improve adhesion between the filler and the thermosettingresin. For example such promoters may be used to coat a silicate fiberor filler to improve adhesion of the resin matrix.

When present, the particulate filler may be used in an amount of about 5to about 95 weight percent, based on the total weight of thecomposition. Within this range, it may be preferable to use aparticulate filler amount of at least about 20 weight percent, morepreferably at least about 40 weight percent, even more preferably atleast about 75 weight percent. Also within this range, it may bepreferable to use a particulate filler amount of up to about 93 weightpercent, more preferably up to about 91 weight percent.

When present, the fibrous filler may be used in an amount of about 2 toabout 80 weight percent, based on the total weight of the composition.Within this range, it may be preferred to use a fibrous filler amount ofat least about 5 weight percent, more preferably at least about 10weight percent, yet more preferably at least about 15 weight percent.Also within this range, it may be preferred to use a fibrous filleramount of up to about 60 weight percent, more preferably up to about 40weight percent, still more preferably up to about 30 weight percent.

The aforementioned fillers may be added to the thermosetting resinwithout any treatment, or after surface treatment, generally with anadhesion promoter.

The curable composition may, optionally, further comprise one or moreadditives known in the art, such as, for example, dyes, pigments,colorants, antioxidants, heat stabilizers, light stabilizers,plasticizers, lubricants, flow modifiers, drip retardants, antiblockingagents, antistatic agents, flow-promoting agents, processing aids,substrate adhesion agents, mold release agents, toughening agents,low-profile additives, stress-relief additives, flame retardants, andthe like, and combinations thereof. Those skilled in the art may selectsuitable additives and determine suitable amounts without undueexperimentation.

There is no particular limitation on the method by which the compositionis prepared, as long as it does not interfere with the ability of thecured composition to absorb less than 1 weight percent water after 7days at 85° C. and 85 percent relative humidity. The composition may beprepared by forming an intimate blend comprising the capped poly(aryleneether) and the olefinically unsaturated monomer. The composition may beprepared from an uncapped poly(arylene ether) by dissolving the uncappedpoly(arylene ether) in a portion of the olefinically unsaturatedmonomer, adding a capping agent to form the capped poly(arylene ether)in the presence of the olefinically unsaturated monomer, optionallywashing the reaction mixture with an aqueous solution, and adding anyother optional components to form the thermoset composition. In oneembodiment, the composition may be prepared by blending an olefinicallyunsaturated monomer, and a capped poly(arylene ether) prepared by thereaction of an uncapped poly(arylene ether) with an anhydride cappingagent and isolated by precipitation with a C₂-C₆ alkanol to form acurable composition; wherein the composition after curing absorbs lessthan 1 weight percent water after 7 days at 85° C. and 85 percentrelative humidity. The C₂-C₆ alkanol preferably comprises isopropanol.In one embodiment, the composition may be prepared by capping thepoly(arylene ether) in solution, washing the solution with an aqueoussolution, separating the washed solution, precipitating the cappedpoly(arylene ether) by combining the washed solution with anantisolvent, drying the capped poly(arylene ether) under vacuum, andadding any other components to form the thermoset composition.

There is no particular limitation on the method by which the compositionmay be cured. The composition may, for example, be cured thermally or byusing irradiation techniques, including radio frequency heating, UVirradiation and electron beam irradiation. For example, the compositionmay be cured by initiating chain-reaction curing with 10 seconds ofradio frequency heating. When heat curing is used, the temperatureselected may be in a range of about 80° to about 300° C. The heatingperiod may be in a range of about 5 seconds to about 24 hours. Curingmay be staged to produce a partially cured and often tack-free resin,which then is fully cured by heating for longer periods or at highertemperatures.

One embodiment is a cured composition obtained by curing any of theabove-described curable compositions. It will be understood that theterm “curing” includes partially curing and fully curing. Because thecomponents of the curable composition may react with each other duringcuring, the cured compositions may be described as comprising thereaction products of the curable composition components.

Another embodiment is an article comprising any of the curedcompositions. The curable composition is useful for fabricating a widerange of articles, and it is particularly suitable for use as anencapsulant for electronic devices. The composition exhibits highlydesirable properties. Reduced water absorption properties are describedabove. In addition, in one embodiment, the cured composition may exhibita UL94 flammability rating of V-1, preferably, V-0. The curedcomposition may exhibit a glass transition temperature of at least 120°C., preferably at least 130° C., more preferably at least 140° C.

The invention is further illustrated by the following non-limitingexamples.

PREPARATIVE EXAMPLE 1

This example describes the preparation of a methacrylate-cappedpoly(2,6-dimethyl-1,4-phenylene ether) having an intrinsic viscosity ofabout 0.12 dL/g. Toluene (30.5 kg), and poly(2,6-dimethyl-1,4-phenyleneether) (30.5 kg; intrinsic viscosity 0.12 dL/g) were combined and heatedto about 85° C. Dimethylaminopyridine (0.420 kg) was added. Once allsolids appeared to dissolve, methacrylic anhydride (3.656 kg) wasgradually added. The resulting solution was maintained at 85° C. forthree hours with continuous mixing. The solution was then cooled to roomtemperature to yield a toluene solution of methacrylate-cappedpoly(2,6-dimethyl-1,4-phenylene ether).

PREPARATIVE EXAMPLE 2

This example describes the isolation of a methacrylate-cappedpoly(2,6-dimethyl-1,4-phenylene ether) by precipitation. A toluenesolution of methacrylate-capped poly(2,6-dimethyl-1,4-phenylene ether)having an intrinsic viscosity of 0.12 dL/g was prepared as described inPreparative Example 1. The methacrylate-cappedpoly(2,6-dimethyl-1,4-phenylene ether) was precipitated by slowly addingtwo liters of the toluene solution to four liters of room temperaturemethanol, which was being vigorously stirred in a blender. The toluenesolution is preferably warmed before addition to the methanol. Warmingreduces the viscosity of the solution. The rate of addition of thetoluene solution to the methanol was slow enough to continuously cause astream of polymer to be precipitated as a fine dispersion, but not sofast as to allow the polymer to coagulate into a continuous strand. Avolume ratio of methanol to toluene solution higher than 2:1 isacceptable, but much lower ratios may sometimes cause clumping andcoagulation of the precipitated polymer. The precipitated polymer wasfiltered, washed with methanol, and dried overnight at 85° C.

PREPARATIVE EXAMPLES 3-9

Methacrylate-capped poly(2,6-dimethyl-1,4-phenylene ether) resins wereisolated by precipitations that varied in the identity of theantisolvent and the method of combining the polyphenylene ether solutionwith the antisolvent. The solution of 50 weight percentmethacrylate-capped poly(2,6-dimethyl-1,4-phenylene ether) (intrinsicviscosity=0.12 dL/g) was prepared by reaction of the correspondinguncapped polyphenylene ether (1406 g) with methacrylic anhydride (188.6g) in toluene solvent (1406 g) with dimethylaminopyridine catalyst (17.9g), as described above.

So-called “normal” precipitations, in which the toluene solution ofcapped polyphenylene ether was poured into the antisolvent, wereconducted as follows. Four hundred milliliters of room temperatureantisolvent (methanol, isopropanol, acetone, or methyl ethyl ketone(MEK)) were added to a WARING® blender equipped with a 1000 mL capacityglass container. While the antisolvent in the blender was agitated, apre-weighed portion of approximately 140 grams of capped polyphenyleneether solution at about 40° C. was added drop-wise, causingprecipitation of the capped polyphenylene ether. The resulting mixturewas poured onto a PYREX® brand Büchner funnel with a coarse fritteddisc, and a filter cake of the precipitated capped polyphenylene etherwas allowed to form. Once a filter cake had formed, vacuum was appliedto the filter to remove solvent. The precipitate was washed with anadditional 50 mL of antisolvent, dried in a vacuum oven for 3.5 hours at130° C., under 20 inches (508 millimeters) of vacuum with a flow ofnitrogen at 15 standard cubic feet per hour (0.425 standard cubic metersper hour). After removal from the oven and cooling to ambienttemperature the material was weighed.

So-called “reverse” precipitations, in which the antisolvent was pouredinto the toluene solution of polyphenylene ether, were conducted asfollows. A pre-weighed portion of approximately 140 grams of cappedpolyphenylene ether solution at about 40° C. was added to the blender.While the contents of the blender were agitated, 400 mL of antisolventwas added over the course of about six minutes, causing precipitation ofthe capped polyphenylene ether. The resulting precipitate was filtered,washed, and dried as described for the “normal” precipitation.

Each precipitated capped polyphenylene ether was characterized bydetermining its molecular weight and residual impurities. Number averagemolecular weight (M_(n)) and weight average molecular weight (M_(w)),each expressed in units of atomic mass units (AMU), were determinedusing GPC (gel permeation chromatography) using polystyrene standards.Residual concentrations of toluene, methacrylic acid, methacrylicanhydride, and dimethylaminopyridine (DMAP), all expressed in ppm, weredetermined by gas chromatography using a flame ionization detector.Residual concentrations of the antisolvents (methanol, isopropanol andacetone), all expressed in ppm, were determined by gaschromatography/mass spectrometry (GC/MS). Results are presented inTable 1. The results show that the reverse method yields lower levels oftoluene and methacrylic acid, and higher levels of DMAP than the normalmethod. The normal method with isopropanol yields an exceedingly andunexpectedly low level of residual methacrylic anhydride. The normalprecipitation with MEK selectively precipitates higher molecular weightcapped polyphenylene ether, but this selectivity comes at the expense ofyield. TABLE 1 Prep. Prep. Prep. Prep. Ex. 3 Ex. 4 Ex. 5 Ex. 6Precipitation normal normal normal normal Method Antisolvent methanolisopropanol acetone MEK Yield (%) 97.3 99.1 64.3 30.9 M_(n) (AMU) 2,8223,051 4,345 6,144 M_(w) (AMU) 7,024 7,191 8,832 11,949 M_(n)/M_(w) 2.492.36 2.03 1.94 Toluene (ppm) 30,711 31,111 25,612 23,595 Methacrylicacid 7,524 6,365 9,595 8,467 (ppm) Methacrylic 57 5 50 850 anhydride(ppm) DMAP (ppm) 371 242 485 258 Methanol (ppm) ND — — — Isopropanol(ppm) — 19,846 — — Acetone (ppm) — — ND — ND = not detected (less than10 ppm for methanol, 100 ppm for isopropanol, and 100 ppm for acetone)Prep. Ex. 7 Prep. Ex. 8 Prep. Ex. 9 Precipitation reverse reversereverse Method Antisolvent methanol isopropanol acetone Yield (%) 97.798.2 70.3 M_(n) (AMU) 3,098.7 3,213.3 4,099.7 M_(w) (AMU) 7,172.77,202.3 8,769.7 M_(n)/M_(w) 2.31 2.24 2.14 Toluene (ppm) 4,174 4,41838,358 Methacrylic acid 1,229 2,097 7,809 (ppm) Methacrylic 185 177 75anhydride (ppm) DMAP (ppm) 738 504 522 Methanol (ppm) ND — — Isopropanol(ppm) — ND — Acetone (ppm) — — 352 ND = not detected (less than 10 ppmfor methanol, and 100 ppm for isopropanol)

PREPARATIVE EXAMPLES 10 AND 11

A 50 weight percent solution of methacrylate-cappedpoly(2,6-dimethyl-1,4-phenylene ether) (intrinsic viscosity=0.12 dL/g)in toluene was prepared as described in the preceding example. Toluenewas removed in a vacuum oven under two conditions: (1) 200° C. for fourhours (Preparative Example 10), or (2) 100° C. for 2 hours (PreparativeExample 11). The non-volatile residue was analyzed to determine cappedpoly(arylene ether) molecular weight and residual toluene, methacrylicacid, methacrylic anhydride, and DMAP. Results are presented in Table 2.The results show that there is a negligible effect on the molecularweight of the capped polyphenylene ether resins when isolated bydevolatilization. TABLE 2 Prep. Ex. 10 Prep. Ex. 11 M_(n) (AMU) 3,2603,260 M_(w) (AMU) 7,240 7,240 M_(n)/M_(w) 2.20 2.20 Toluene (ppm) 1,17928,405 Methacrylic acid (ppm) 1,322 23,167 Methacrylic anhydride (ppm)930 668 DMAP (ppm) 68 88

PREPARATIVE EXAMPLES 12-23

To reduce the amount of residual impurities, isolations were performedwith a water wash prior to devolatilization. The solution ofmethacrylate-capped poly(2,6-dimethyl-1,4-phenylene ether) in toluenewas warmed to a pre-determined temperature then mixed for 30 seconds byhand with an amount of warmed water. The mixture was centrifuged at20,000 rotations per minute for two minutes and the organic layer wasrecovered. The organic layer was dried for 4 hours at 120° C. in avacuum oven. The resulting powders were analyzed for methacrylic acid(MA), methacrylic anhydride (MAA), dimethylaminopyridine, and toluene.The washing conditions and results are shown in Table 3. TABLE 3 Amt PPEin Mixing Water/ solution Temp. Organic MA MAA DMAP Toluene (wt %) (°C.) Ratio (ppm) (ppm) (ppm) (ppm) Prep. Ex. 12 20 21 1 6909 208 32153670 Prep. Ex. 13 20 21 2 5978 190 304 54790 Prep. Ex. 14 20 50 1 3310466 220 21380 Prep. Ex. 15 20 50 2 2668 298 196 19700 Prep. Ex. 16 35 211 9254 293 164 48380 Prep. Ex. 17 35 21 2 8740 423 144 57810 Prep. Ex.18 35 50 1 9134 454 113 50270 Prep. Ex. 19 35 50 2 6627 432 111 53290Prep. Ex. 20 50 21 1 24990 346 36 59750 Prep. Ex. 21 50 21 2 25003 35834 55070 Prep. Ex. 22 50 50 1 9211 329 91 56830 Prep. Ex. 23 50 50 26680 285 96 53560The results show that a higher polyphenylene ether concentration insolution, higher mixing temperature, and higher water/organic ratio eachimprove (decrease) the concentrations of residual compounds in theisolated polyphenylene ether resin.

COMPARATIVE EXAMPLES 1-7

Seven compositions were prepared and molded. They all usedmethacrylate-capped poly(2,6-dimethyl-1,4-phenylene ether) resinsprovided as capping reaction mixtures in styrene that varied in theconcentrations of methacrylic anhydride and dimethylaminopyridineemployed in the capping reactions. Molar ratios of methacrylic anhydrideto polyphenylene ether free hydroxyl groups and dimethylaminopyridine topolyphenylene ether free hydroxyl groups are given in Table 4. Thepercent conversion of uncapped polyphenylene ether to cappedpolyphenylene ether was determined for each capping reaction mixture bycomparing the free hydroxyl end group contents of the uncappedpolyphenylene ether resin and the capped polyphenylene ether resin inthe reaction mixture. The free hydroxyl end group contents weredetermined by functionalization with a phosphorus reagent and ³¹P NMR asdescribed in P. Chan, D. S. Argyropolis, D. M. White, G. W. Yeager, andA. S. Hay, Macromolecules, 1994, volume 27, pages 6371 ff. The uncappedpolyphenylene ether resin had a free hydroxyl end group content of0.1658 weight percent.

All molding compositions contained 29.2 weight percentmethacrylate-capped polyphenylene ether, 54.1 weight percent styrene,14.7 weight percent trimethylolpropane trimethacrylate, and 2.0 weightpercent t-butyl peroxybenzoate. Molding compositions were prepared bymixing the styrene solution of methacrylate-capped polyphenylene etherwith trimethylolpropane trimethacrylate and heating on a water bathuntil the components appeared well blended. The mixture was then heatedto 140° C., degassed under vacuum for about ten minutes, and cooled toabout 80-100° C. before t-butyl peroxybenzoate was added. Thecomposition was then poured into a mold cavity and cured for 60 minutesat 90° C. followed by 60 minutes at 150° C.

Molded samples were pre-weighed, then immersed in boiling water andreweighed after one, four, and five days. Weight change values representaverages for three samples at each condition. Compositions and waterabsorption properties are summarized in Table 4. The results show thatwater absorption by cured samples was positively correlated with theconcentrations of methacrylic anhydride and dimethylaminopyridine in thecapping reaction mixture. The results further show that when theconcentrations of methacrylic anhydride and dimethylaminopyridine wereincrementally reduced, the extent of conversion of uncapped to cappedpolyphenylene ether was reduced, and the curing properties of thecomposition were compromised. It is therefore difficult to achieveessentially complete capping of the polyphenylene ether without using asubstantial excess of the capping agent.

It was also observed that the transparency of the cured composition wasinversely proportional to the concentration of methacrylic anhydride anddimethylaminopyridine used in the capping reaction mixture. In otherwords, cured disks prepared from capping mixtures having lowconcentrations of methacrylic anhydride and 4-dimethylaminopyridineexhibited low coloration and high transparency, whereas those preparedfrom capping mixtures having high concentrations exhibited highercoloration and lower transparency. TABLE 4 C. Ex. 1 C. Ex. 2 C. Ex. 3Compositions Initial concentration of DMAP in PPE 1.38 0.69 0.69 cappingreaction mixture (wt %) Initial concentration of MAA in PPE 12.0 6.006.00 capping reaction mixture (wt %) Molar ratio of MAA:OH 21.3 10.610.6 Molar ratio of DMAP:OH 3.25 1.62 1.62 Conversion of uncapped tocapped PPE 100.0 100.0 100.0 in capping reaction mixture (%) PropertiesCuring behavior cured cured cured well well well Weight gain after 1 dayin boiling 1.80 1.01 0.99 water (%) Weight gain after 4 days in boiling2.70 1.30 1.28 water (%) Weight gain after 5 days in boiling 2.81 1.361.33 water (%) C. Ex. 4 C. Ex. 5 C. Ex. 6 Compositions Initialconcentration of DMAP in PPE 0.35 0.21 0.21 capping reaction mixture (wt%) Initial concentration of MAA in PPE 3.00 1.76 1.00 capping reactionmixture (wt %) Molar ratio of MAA:OH 5.32 3.12 1.77 Molar ratio ofDMAP:OH 0.81 0.50 0.50 Conversion of uncapped to capped PPE 100.0 97.562.3 in capping reaction mixture (%) Properties Curing behavior curedcured cured well well slowly, incompletely Weight gain after 1 day inboiling 0.80 0.51 — water (%) Weight gain after 4 days in boiling 0.950.51 — water (%) Weight gain after 5 days in boiling 1.00 0.53 — water(%) C. Ex. 7 Compositions Initial concentration of DMAP in PPE capping0.21 reaction mixture (wt %) Initial concentration of MAA in PPE capping0.66 reaction mixture (wt %) Molar ratio of MAA:PPE-OH 1.17 Molar ratioof DMAP:PPE-OH 0.50 Conversion of uncapped to capped PPE in capping 36.1reaction mixture (%) Properties Curing behavior did not cure Weight gainafter 1 day in boiling water (%) — Weight gain after 4 days in boilingwater (%) — Weight gain after 5 days in boiling water (%) —

EXAMPLES 1 AND 2

Two compositions were prepared, varying in the presence or absence of asilane coupling agent. The methacrylate-cappedpoly(2,6-dimethyl-1,4-phenylene ether) (MA-PPE) either had an intrinsicviscosity of 0.30 dL/g (Example 1) or was a blend of 0.12 dL/g and 0.30dL/g materials (Example 2). These polymers were isolated byprecipitation using a procedure similar to that described in PreparativeExample 2. Fused silicas were obtained from Denrla as FB570 and SPF30.The silane coupling agent methacryloxypropyl trimethoxysilane (MAPTMS)was obtained from Dow Corning as Z-6030. The acryloyl monomerethoxylated (2) bisphenol A dimethacrylate was obtained as SR-348 fromSartomer. An aluminophosphorus flame retardant was obtained as OP930from Clariant. A mold release agent was obtained as LICOWAX® OP fromClariant. For Example 2, the silane coupling agent was incorporated intothe composition by pre-blending with the two fused silicas and exposingthe resulting mixture to two hours at 85° C. before mixing it with theremaining components. Cured disks were prepared by compression moldingthe composition for ten minutes at 160° C. and further cured for twohours at 175° C. Bars having dimensions one-eighth inch (0.3175centimeter) by one-half inch (1.27 centimeters) by four inches (10.16centimeters) were cut from the disks. Bars were dried for one hour at115° C., then weighed, exposed to 85° C. and 85% relative humidity (RH)for times ranging from one to seven days, then reweighed. Compositionsand water absorption results are given in Table 5. Component amounts areexpressed in parts by weight. The weight changes in Table 5 areexpressed as a percentage increase in weight relative to the original,pre-dried weight of the sample. The results show that both samplesabsorbed less than 0.2 weight percent water after seven days at 85° C.and 85% relative humidity. TABLE 5 Ex. 1 Ex. 2 MA-PPE, 0.12 dL/g — 6.13MA-PPE, 0.30 dL/g 15.75 9.62 Ethoxylated (2) bisphenol A dimethacrylate52.76 52.76 Pigment 0.24 0.24 Dicumyl peroxide 1.97 1.97 4-t-Butylcatechol 0.16 0.16 Fused silica, FB570 398.1 398.1 Fused silica, SFP30M44.2 44.2 Methacryloxypropyl trimethoxysilane — 3.93 Flame retardant7.88 7.88 Mold release agent — 2.10 Water absorption after 1 day (%)0.0811 0.1159 Water absorption after 2 days (%) 0.1186 0.1375 Waterabsorption after 3 days (%) 0.1366 0.1527 Water absorption after 7 days(%) 0.1482 0.1619

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing fromessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

All cited patents, patent applications, and other references areincorporated herein by reference in their entirety.

1. A curable composition, comprising: a capped poly(arylene ether)prepared by the reaction of an uncapped poly(arylene ether) with ananhydride capping agent; wherein the reaction of an uncappedpoly(arylene ether) with an anhydride capping agent is conducted in asolvent to form a solution of the capped poly(arylene ether); andwherein the solution of the capped poly(arylene ether) is washed with anaqueous solution; and an olefinically unsaturated monomer; wherein thecomposition after curing absorbs less than 1 weight percent water after7 days at 85° C. and 85 percent relative humidity.
 2. The curablecomposition of claim 1, wherein the aqueous solution has a pH of about 1to about
 7. 3. The curable composition of claim 1, wherein the aqueoussolution has a pH of about 7 to about
 13. 4. The curable composition ofclaim 1, wherein the aqueous solution comprises sodium hydroxide.
 5. Thecurable composition of claim 1, wherein the aqueous solution compriseshydrochloric acid.
 6. The curable composition of claim 1, the solutionof the capped poly(arylene ether) is washed with an acidic aqueoussolution and a basic aqueous solution.
 7. The curable composition ofclaim 1, wherein the composition comprises less than 50 parts permillion by weight of the anhydride capping agent, based on the weight ofthe capped poly(arylene ether).
 8. The curable composition of claim 1,wherein the composition comprises less than 1 weight percent, based onthe weight of the capped poly(arylene ether), of a free acid obtained onhydrolysis of the anhydride capping agent.
 9. The curable composition ofclaim 1, wherein the reaction of the uncapped poly(arylene ether) withthe anhydride capping agent is performed in the presence of an organicamine catalyst, and wherein the composition comprises less than 1,000parts per million by weight of the organic amine catalyst, based on theweight of the capped poly(arylene ether).
 10. The curable composition ofclaim 1, wherein the capped poly(arylene ether) has the formulaQ(J-K)_(y) wherein Q is the residuum of a monohydric, dihydric, orpolyhydric phenol; y is 1 to 100; J comprises repeating structural unitshaving the formula

wherein R¹ and R³ are each independently selected from the groupconsisting of hydrogen, halogen, primary or secondary C₁-C₁₂ alkyl,C₂-C₁₂ alkenyl, C₂-C₁₂ alkynyl, C₁-C₁₂ aminoalkyl, C₁-C₁₂ hydroxyalkyl,phenyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ hydrocarbyloxy, and C₂-C₁₂halohydrocarbyloxy wherein at least two carbon atoms separate thehalogen and oxygen atoms; R² and R⁴ are each independently selected fromthe group consisting of halogen, primary or secondary C₁-C₁₂ alkyl,C₂-C₁₂ alkenyl, C₂-C₁₂ alkynyl, C₁-C₁₂ aminoalkyl, C₁-C₁₂ hydroxyalkyl,phenyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ hydrocarbyloxy, and C₂-C₁₂halohydrocarbyloxy wherein at least two carbon atoms separate thehalogen and oxygen atoms; m is 1 to about 200; and K is a capping groupselected from the group consisting of

wherein R⁵ is C₁-C₁₂ hydrocarbyl optionally substituted with one or twocarboxylic acid groups; R⁶—R⁸ are each independently selected from thegroup consisting of hydrogen, C₁-C₁₈ hydrocarbyl, C₂-C₁₈hydrocarbyloxycarbonyl, nitrile, formyl, carboxylic acid, imidate, andthiocarboxylic acid; R⁹—R¹³ are each independently selected from thegroup consisting of hydrogen, halogen, C₁-C₁₂ alkyl, hydroxy, amino, andcarboxylic acid.
 11. The curable composition of claim 1, wherein thecapped poly(arylene ether) comprises a methacrylate-cappedpoly(2,6-dimethyl-1,4-phenylene ether).
 12. The curable composition ofclaim 1, wherein preparing the capped poly(arylene ether) comprisesprecipitating the capped poly(arylene ether) from an antisolventcomprising a C₂-C₆ alkanol.
 13. The curable composition of claim 12,wherein the antisolvent comprises isopropanol.
 14. The curablecomposition of claim 1, wherein preparing the capped poly(arylene ether)comprises isolating the poly(arylene ether) by devolatilization.
 15. Thecurable composition of claim 1, further comprising about 75 to about 95weight percent of a particulate filler, based on the total weight of thecomposition.
 16. The curable composition of claim 15, wherein theparticulate filler is fused silica.
 17. A curable composition,comprising: a capped poly(arylene ether) prepared by the reaction of anuncapped poly(arylene ether) with an anhydride capping agent; whereinthe reaction of an uncapped poly(arylene ether) with an anhydridecapping agent is conducted in a solvent to form a solution of the cappedpoly(arylene ether); wherein the solution of the capped poly(aryleneether) is washed with an aqueous solution; and wherein the cappedpoly(arylene ether) is isolated by a procedure comprising precipitationwith isopropanol; an olefinically unsaturated monomer; and a particulatefiller; wherein the composition after curing absorbs less than 0.5weight percent water after 7 days at 85° C. and 85 percent relativehumidity; and wherein the composition comprises less than 50 parts permillion by weight of the anhydride capping agent, based on the weight ofthe capped poly(arylene ether).
 18. A curable composition, comprising:about 1 to about 23 weight percent of a methacrylate-cappedpoly(2,6-dimethyl-1,4-phenylene ether) prepared by the reaction of anuncapped poly(2,6-dimethyl-1,4-phenylene ether) with methacrylicanhydride; wherein the reaction of an uncappedpoly(2,6-dimethyl-1,4-phenylene ether) with methacrylic anhydride isconducted in a solvent to form a solution of the methacrylate-cappedpoly(2,6-dimethyl-1,4-phenylene ether); wherein the solution of themethacrylate-capped poly(2,6-dimethyl-1,4-phenylene ether) is washedwith an aqueous solution; and wherein the methacrylate-cappedpoly(2,6-dimethyl-1,4-phenylene ether) is isolated by a procedurecomprising precipitation with isopropanol; about 1 to about 23 weightpercent of an acryloyl monomer comprising at least two acryloylmoieties; about 1 to about 23 weight percent of an alkenyl aromaticmonomer selected from the group consisting of styrene, α-methylstyrene,2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-t-butylstyrene,3-t-butylstyrene, 4-t-butylstyrene, 1,3-divinylbenzene,1,4-divinylbenzene, 1,3-diisopropenylbenzene, 1,4-diisopropenylbenzene,styrenes having from 1 to 5 halogen substituents on the aromatic ring,and combinations thereof; and about 75 to about 95 weight percent offused silica; wherein all weight percents are based on the total weightof the composition; and wherein the composition after curing absorbsless than 0.2 weight percent water after 7 days at 85° C. and 85 percentrelative humidity; and wherein the composition comprises less than 50parts per million by weight of the anhydride capping agent, based on theweight of the capped poly(arylene ether).
 19. A cured compositioncomprising the reaction products obtained on curing the curablecomposition of claim
 1. 20. A cured composition comprising the reactionproducts obtained on curing the curable composition of claim
 17. 21. Acured composition comprising the reaction products obtained on curingthe curable composition of claim
 18. 22. An article comprising the curedcomposition of claim
 19. 23. An article comprising the cured compositionof claim
 20. 24. An article comprising the cured composition of claim21.
 25. A method of preparing a curable composition, comprising:blending a capped poly(arylene ether) and an olefinically unsaturatedmonomer to form a curable composition; wherein the capped poly(aryleneether) is prepared by a process comprising reacting an uncappedpoly(arylene ether) with an anhydride capping agent in a solvent to forma solution of the capped poly(arylene ether); wherein the solution ofthe capped poly(arylene ether) is washed with an aqueous solution; andisolating the capped poly(arylene ether) by precipitation with a C₂-C₆alkanol; and wherein the composition after curing absorbs less than 1weight percent water after 7 days at 85° C. and 85 percent relativehumidity.
 26. The method of claim 25, wherein the C₂-C₆ alkanolcomprises isopropanol.